Rapid X-ray brightening of XTE J1701-462

ATel #15602; Amar Deo Chandra (IISER Kolkata)
on 9 Sep 2022; 07:54 UT
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Credential Certification: Amar Deo Chandra (amar.deo.chandra@gmail.com)

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A likely new outburst from the NS-LMXB XTE J1701-462 was detected by the MAXI/GSC on 2022 September 06 (ATel# 15592) and was confirmed using Swift/XRT observations (ATel# 15594). Swift/XRT follow-up observations were performed in Windowed Timing (WT) mode on 2022 September 7 (MJD 59829) beginning at 11:52:02 for a total exposure time of 1 ks. The average XRT count rate during the observation was 50 counts/s. The maximum XRT count rate detected during the observation was 75 counts/s. The WT mode spectrum is well described by an absorbed power-law with photon index = 1.82 +/- 0.04, with absorption N_H = 2.59 +/- 0.06 x 10^22 cm^-2. High absorption (N_H = 2.7 +/- 0.1 x 10^22 cm^-2) was also reported from Swift/XRT spectral analysis during 2006 January outburst of the source (ATel# 704). The inferred absorbed flux in the 0.3-10 keV band is about 4.15 x 10^-9 erg/s/cm^2. The X-ray luminosity is ~3.8 x 10^37 erg/s for a distance of 8.8 kpc.

The source was again observed by Swift/XRT on 2022 September 8 (MJD 59830) in WT mode beginning at 00:49:00 for a total duration of about 1.4 ks. The average and maximum XRT count rate detected during the observation was 56 counts/s and 108 counts/s respectively. The increase in count rate compared to the Swift/XRT observation on 2022 September 7 suggests brightening of the source. The WT mode spectrum is well described by an absorbed power-law with photon index = 1.60 +/- 0.03, with absorption N_H = 2.51 +/- 0.06 x 10^22 cm^-2. The inferred absorbed flux in the 0.3-10 keV band is about 5.1 x 10^-9 erg/s/cm^2. The X-ray luminosity is ~4.7 x 10^37 erg/s for a distance of 8.8 kpc. The enhancement in X-ray luminosity is about 1.2 times compared to that on 2022 September 7 (MJD 59829) suggesting brightening of the source. Similar brightening of the source by about 1.2 times was observed by RXTE (in the 2-10 keV and 10-40 keV energy bands) during initial few days of the 2006 January outburst (ATel# 703).

The source became brighter in the latest available daily averaged MAXI/GSC observations on 2022 September 8 (MJD 59830.50) having flux of 214 +/- 10 mCrab (4-10 keV energy band) compared to the MAXI/GSC transit observations on 2022 September 5-6 having averaged flux of 124 +/- 8 mCrab in the 4-10 keV energy band (ATel# 15592). The enhancement in the 4-10 keV averaged flux by about 1.7 times suggests rapid brightening of the source in X-rays over the duration of about 3 days.

Follow-up multi-wavelength observations are encouraged.

We thank the Swift Team and Observatory Duty Scientists who made these observations possible. This research has made use of the MAXI data provided by RIKEN, JAXA and the MAXI team.

MAXI observations of XTE J1701-462